This invention relates to an optical velocity measuring apparatus for non-contact measurement type capable of optically measuring the velocity of an object moving relative to another, for example, the velocity of an automotive vehicle moving relative to a road surface, without making any physical contact with the road surface.
A known apparatus of this kind has comprised a first light sensor and a second light sensor disposed in a relation spaced apart by a predetermined distance from each other in a direction of traveling movement of a first object relative to a second object (which is, for example, a road surface) utilized for the measurement of the velocity of the first object relative thereto, an optical system for directing rays of light reflected from the surface of the second object toward the first and second light sensors which convert the incident rays of light into electrical signals, and means for evaluating the correlation (the time lag) between the electrical output signal from the first light sensor and that from the second light sensor thereby determining the velocity of the first object relative to the second object. In the prior art apparatus of this kind having such a construction, the optical system directing the rays of light reflected from the surface of the second object toward the first and second light sensors has included a single lens disposed in common to the first and second light sensors.
In an application of such a prior art optical velocity measuring apparatus of non-contact measurement type to an object such as an automotive vehicle, extreme difficulty has been encountered in the desired accurate measurement of the velocity of the vehicle when the vehicle is being accelerated or decelerated or traveling on a rough road, since the height of the vehicle is not maintained constant in such a case.